Sadly, I agree that a huge, global catastrophic event, or series of catastrophic events would be the only real hope for renewal...
When will it happen?
The planet would clean itself up, for the most part, in a few hundred years or so... a few pockets of human survivors would repopulate and compete with other surviving life forms... perhaps new species will be born out of genetic mishap... who knows...
It has happened before, and this is not the first, or second time, but you have heard me state that too.